1. Field of the Invention
The present invention relates to a machine tool which automatically carry out rebel shifts of stator winding of an AC machine.
2. Disclosure of the Prior Arts
It has been well-known that the stator winding of a large size synchronous machine is prepared by twisting many component wires (insulated rectangular type wires) as rebel shifting, in order to prevent a loss caused by eddy current. In many cases, the shape of the stator winding is in a diamond coil shape and the insulated diamond coil is put in each open slot of the stator.
It has been usual to rebel-shift a bundle of component wires by a hand operation or by using a machine tool for twisting component wires by turning slowly a disc holding a drum of the component wires while taking out the component wires.
In the latter case using the machine tool, the stepping of the component wires is carried out for each pitch by pressing the component wires.
Referring to the drawings, the conventional stepping operation will be illustrated.
In the drawings, the same references designate identical or corresponding parts and a hatch for a sectional view is eliminated so as to be easily understood in certain drawings.
FIG. 1 shows a bundle of component wires treated by the rebel shifting and FIG. 1(a) is a sectional view perpendicular to the component wires and FIG. 1(b) is a sectional view parallel to the component wires. The reference numeral (100) designates a bundle of component wires which are arranged in two rows extending in a row direction and several lines extending in a line direction; (200) designates an insulator between two rows and (300) designates an insulator for a shifted wire (hereinafter referring to a S-insulator). As shown in FIG. 1(b), the component wire of the bundle (100) is shifted from the lower row to the upper row and the other component wire is shifted from the upper row to the lower row (the latter is not shown in FIG. 1(b)). The shifting point of the adjacent component wire is departed for one pitch shown as P in FIG. 1(b). The component wire is also shifted in the lines at the shifting point for the row whereby the component wires of the bundle are alternatively shifted.
In order to prepare such structure of the bundle of component wires by a hand operation, it is necessary to carry out the stepping of the component wires first.
FIG. 2 is a side view of a part of the stepped component wires. The stepped height W is equal to the sum of the width of the component wire and an insulator (200) between the rows and the distance between the shifting points of the adjacent component wires is one pitch P which is usually 50 mm to 100 mm.
When number of the lines of the component wires is N, and the stepped-bending of the component wires is carried out the component wire shifted is returned to the original condition at the distance departed for NP from the shifted point. Thus, the shaped component wires for one row are disposed on a table so that the edges are upper and the central parts are lower. The edge of the component wire which has the longest non-contacting portions, is lifted up and is crossed over the other bent component wires and is put on the opposite side. Then, the adjacent component wire is moved in the same manner in sequence. After finishing edges of the component wires in one side, the edges of the component wires in the other side are moved in the same manner from the longest non-contacted component wire in sequence.
In the operation, the non-contacted parts which should be lifted are sometimes about 4 m and the component wires are thin and easily bent. Accordingly, sometimes, it is necessary to lift up the component wire by three to four persons. The hand operation is simple but requires the labour work by many persons.
The other component wires in the other row are combined in the same manner. The former grouped component wires are turned over to cover on the latter grouped component wires and the edges of non-contacted parts of the latter grouped component wires are shifted on the contacted portion of the component wires. The other edges of the grouped component wires are also shifted in the same manner. The insulator between the rows (200) is inserted after the shifting operation. The hand operation is quite complicated as described. Moreover, in the operation, it is necessary to treat the component wires by stepped bending. The component wires for each row are previously combined and then, the two grouped component wires for two rows are further combined. Accordingly, it is evident for a hand operation that the rebel shifting can be attained only for a simple half coil prepared by carrying out the stepped combination for straight portions of the component wires and then bending the coil ends to curve them. Thus, the curved bundle of component wires or the bundle of component wires whose one ends are fixed such as one turn full coil or the coil ends could not be treated by the rebel shifting.
The half coil is prepared by cutting off both of noses of the diamond coil.
The one turn full coil is prepared by cutting off one end of the nose of the diamond coil. The rebel shifting is performed in the slot part.
The coil end means the part having relatively slight curve from the straight part of the slot part to the nose part.
The conventional machine disposing many drums of the component wires on a disc table has been used for a small number of the component wires in one bundle.
When the number of the component wires are 40 to 150 as a stator coil of a rotary machine, the number of the drums of the component wires is great. Accordingly, such machine has not been used in the fields of coils of rotary machines.
The disadvantages of the conventional methods are as follows.
(a) it is operation requiring many steps and greater labour costs
(b) the stepped combination could be attained only for straight component wires; and
(c) it is necessary to combine an insulator between rows.
The operation for inserting the insulator for shifted wire (6) is carried out after the stepping operation. That is, the component wires are bent and shifted, a spatula having a thin edge of a width of 10 mm and a thickness of 5 mm is inserted into a gap under the component wire (10) which has been bent and shifted and an insulator for shifted wire (6) having a predetermined size is inserted into the space. The insulator for shifted wire (6) is a sheet having a thickness of 0.1 to 0.2 mm on which mica is bonded.
It takes about 10 second to shift one part and accordingly, it takes about 30 to 60 minutes for one coil.
Thus, the stepped combination is a simple work but it requires a long labour time and many persons to be low productivity, disadvantageously.